1995 F150 5.0 idle/drive issues

[Eliteman76]

OK, been a while since I've posted, but could just use some help.

I picked up said truck beginning of this year for my daily:


This is a mass airflow efi truck from what I have been told. For around 50% of the time, runs great for something with 200K on the clock. Occasional lifter tick and that's about it.

I had to replace the rear tank pump, and installed the syphon kit onto the pumps to hopefully cure some of the issues this generation was known for.
Replaced the fuel filter as the true was acting like it was starving for fuel, and the filter was honestly plugged up. First filter I've pulled and it was seriously around 5#.

Issue on the truck:
Starting up cold, and truck will run, drive, act normal.
Once warmed up, 5-10 minutes into my drive the truck acts like it goes into limp mode. Power goes down severely, and the only thing that works is basically stomping it WOT and it'll take off, drive normal for a while, and start to surge, stutter, etc. I have feathered the gas pedal and once again this seems to work slightly.

I have yet to test fuel pressure on the engine.
CEL pops on randomly.

I had a trans shop check the E40D out, thinking maybe it was shot, but they pulled a Purge canister code off the pcm. The trans shop, which I trust their call, points to lack of fuel.

Truck occasionally has been stalling on me. Can be at a light, drive through, or bad traffic. The truck on occasion will surge, and the whole truck lurches forward.
{Which is why I assumed trans issues at first}

Leads me to here:
Test PSI off rail?
Fuel pressure regulator possible culprit?

Another thing I noticed:
Passenger side frame rail, their is a line running from front to back, unsure if this is a return line. Noticed it has a dent across the line. Wondering some chance this is an issue?

Just getting frustrated and need some guidance. My Chiltons manuals are lacking...but they are a basic guide anyways and not worth much help.

I actually like this truck, despite the fact I still like my '79 highboy...but not much good if it's -20 F in Nebraska january in a snow storm and it dies on me.

[Beagle]

Good to hear from you Andrew, hope all is well.

I'd stay after the codes, it sounds like it's gone into limp. I'm speaking to an SD truck here, I haven't looked at an MAF one but they shouldn't be much different.

The fuel will be 39ish at the rail, should have a return off the back right side if I remember. They both come up the driver side. The "tick" sound may be number 4, where it's actually trying to suck the intake gasket and may have burned a valve by now. It will run lean as hell.

Did you sell the other one? I'm wondering if the O2's have ever been replaced, but before tossing parts at it I'd get all of the codes. Probably would not hurt to clean the IAC for idle, but that shouldn't impact anything else.

I believe a TBI Camaro fuel pump fits the pressure pump holder perfectly. Perfomer and 600 CFM something, ebay HEI. Wait... that's not what you asked. oops. Do you have a code reader?

I'd be interested to know if it's fussing about the EGR valve, which should be nice and nasty by now.

[milner351]

check for cracked gasket between the upper and lower parts of the intake manifold - I had an 88 and a 92 both have weird issues not too different from what you describe - pulled the uppers to replace injectors, and found the gaskets damaged, trucks both ran much better with new gaskets under top intake and at throttle body - also check that IAC valve is not all gunked up.

[Beagle]

you know the IAC is gunked up. You can't get around the block without them turning black. lol. The passenger side intake gasket at the head is where mine melted down and it had been "replaced" by one of those certied types. I cringed when it came apart. The upper was pinched too, forgot about that. How it ran as well as it did for several years is beyond me. (gave it to somebody who gave it to somebody else who gave it back to me... and I yanked it when an old lady on a Vespa blew me away at a stop light. lol.)

The bucking stalling thing would head me towards the EGR though - not sure what it takes for them to throw a code other than absence. Mine was pretty cruddy at 200+ but I pulled all of it and put a Performer/600 holley/ebay HEI and Camaro TBI pump on it with a cheapy deadhead regulator.

Anything on the passenger side is probably canister or air pump related iirc.

[Slick68]

First off, I'm pretty sure that truck has a Speed Density system instead of MAF. The only trucks of that era with MAF systems were the Lightnings. My 94 had similar symptoms after I first got it. My buddy was a Ford tech at the time I bought it, so the first thing thing we did was chuck the whole EGR system. Keep in mind if you do this, you will have to retain the AIR pump as there is no way to reroute the belt. Mine just pumped air back into the atmosphere. lol We also replaced the IAC, the TPS sensor, and removed and cleaned the throttle body. That seemed to fix it, but the poor truck still ran like a total turd. With that many miles, and the condition of the filter, I would recommend replacing the injectors. Don't have them cleaned out unless they're reverse flow cleaned.

[Beagle]

Nah, None of the Gen 1 (93-95) lightnings were MAF... All of the Gen ii's (1999-2004) were MAF/ODBii and they'll tell you what ails them. lol. ODBI is a crapshoot. There were a few MAF Cali F150 trucks and Broncos 94-96ish. There was a conversion kit for the Lightning that was something like 800.00 , NLOC.NET if you want details on it.

I'm leaning more and more towards thinking EGR would be a good thing to have a look at first. There's an air diverter valve for the air pump gunk, (TAD) that might be worth looking into also.

[Russell]

I had a 95 with the 300 I6 that would buck at highway cruise. I did alot of reading on the internet and what everyone said was ford had to put too much exhaust back into the motor to meet emissions. "They" said the best thing to do was put a reducer in the EGR pipe to limit the flow. If you block the EGR it might run lean / worse. I never tried to fix it. Then again the 4.9 and 5.0 may not have the same problems.

P.S sold truck to buy cummins turbo diesel

[Eliteman76]

Thanks guys.
I'm going to spend some time this weekend setting up with a bypass wire and run it through the sequence to see what codes I can pull w/o buy a code scanner.

I had Bill here, and a few other guys point out to their surprise it's a MAF truck. Late 95 build.




It's not set up like alot of the other F series in 92-94 that I've seen at the yards, the throttle body is different, the air box is different.

Also, after reading threads on the FTE Ford Truck Enthusiast forum, I am thinking I may be getting a backfire in the plenum randomly...I've gotten some odd "pop pop" noises, and was not sure where I was getting that.
I have also been smelling gasoline fumes. Mainly at the back of the truck. Assuming maybe a bad gas cap. Unsure though.

I didn't think about the IAC, had that issue on our contour. I really was trying to avoid tearing too deep into this but better it be now and not the dead of January.

[JeffMcKC]

The IAC wont reall make it run better at WOT only then back down be ok for a bit, I have seen 3 different fuel systems in 95 the in tank only fuel pumps if thats it then switch tanks problem solved, the 2 lift pump one main when a lift pump goes bad then the main will suck air past the fuel line o-rings, switch tanks problem solved, the single main pump never seen one go bad, that ran. BUTTTTTT they also had different fuel filter systems the "TOLL FREE" Fords 1-800 part number and some had in the bottom of a plastic screw on bottom a paper filter no one ever changed. These cause some very weird stuff. AT WOT the PCM goes to open loop no EGO help. If you dont have a EGR code on KOEO or KOER test you dont have a EGR issue. Unless the exhaust is plugged forcing more air threw the EGR. These where very bad about cross fire on plug wire nocking rod bearings out, and the Converters shuddering on lock up about 45 mph which when tipped in will release and add power. When the plenum gasket sucks they idle real high with the vaccum leak


For the guy with the 4.9 if it was a stick shift and it was up hill high load light throttle, it feels like a plug wire almost, unplug the
EGR if the miss goes away then its the injectors. They get restricted you can 4 X the cleaner and 3 to 4 Tanks of fuel it seems to get rid of it

[anotheridiot]

Might sound a little off, but you still got the bent parts? your computer is close by the damaged area isnt it? you check all the wiring within that area to check for shorts from the scrunch?

[Eliteman76]

When I pulled the truck apart, no issues with the loom that we could tell.
When I first started driving the truck, I was not having this sort of issue. Seems like it's gradually been coming on.

I have a couple basic plans of attack. I'm hate the idea of tossing parts at anything without understanding what's going on.
I am starting to consider it may need a tune up as honestly, I bought a wrecked truck and not a good idea on the history. Hell I originally bought this for the engine and tires.

I'm going to test the truck this weekend and see what mess of codes it kicks out.

On the truck, it's strictly an in tank pump unit.
I did read on FTE about some guys experiencing really odd issues of the valve on the frame, and basically one tank would dump off into other tank.I don't think this is an issue, but hard to know.
Concerning pumps: When bought, rear tank was DOA. Running front tank only.
I picked up a bunch of stuff off a kid parting a 94 302, basic twin to mine, ext cab, 302, 4x4. Exhaust, leaf springs, front gas tank and pump, rear smashed tank and pump.

Anyways...going to do some testing this weekend and will report back.

[Eliteman76]

OK. Ran over to O'Reilly Auto Parts, used scan tool.

After running the KOER test twice, kicked back:
DTC 583
DTC 412
DTC 172

538 - Insuf. RPM change during KOER test.
Read on this code, seems to point to either non-issue, or TPS sensor. I know at times with my truck it seems a bit slow to take off. Almost as if in 2nd gear.

412 - Can't control RPM
Pointing to TPS sensor?

172 - HEG H)23 Sensor. Fault/Lean
Looking like O2 sensor, which has been on the to-do list regardless.
Also read other seem to suffer dirty MAF element.
{Note-what sprays are MAF safe? I did notice looking over the intake pictures during my teardown and rebuild, the airbox was filthy and had a clogged air filter before I replaced.

I stopped in at an autozone to snag a new gas cap for the rear tank, and discussing with the manager there, and he also mentioned tapping on the MAF to see if the element was going. No such luck.

Did also get Vapor purge canister valve bad/failed message off the scanner.
I was looking, and this part looks to be new on my engine, before I got the truck.

[Teddyzee]

Insufficient rpm change and can't control idle sounds like it may be idling too high? When the IAC is operated during the test, it's unable to slow the RPM (as the IAC can only raise idle).
Try adjusting the idle screw. Did you clean the IAC? Is the IAC plugged in? Did you find a vacuum leak?
When you're having the problem, does it go away if you unplug the MAF meter?
The TPS is pretty fool proof. It should read around 1v with the throttle closed and key on. You can loosen the screws and twist it slightly in the screw holes to adjust. The TPS value obviously changes slightly as you adjust the idle screw.